1. Field of the Invention
The present invention pertains to land-based seismic surveying and, in particular, to reliable broadcast delivery of communications in land-based seismic surveys.
2. Description of the Related Art
This section of this document is intended to introduce various aspects of the art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. As the section's title implies, this is a discussion of related art. That such art is related in no way implies that it is also prior art. The related art may or may not be prior art. It should therefore be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Seismic surveying typically involves imparting seismic survey signals into the Earth. Various features in the subterranean formations reflect the signals back to the Earth's surface. The reflections are then detected and recorded. Analysis of the recorded reflections can then yield indications of probable presence (or absence) of hydrocarbon deposits and their locations.
Seismic surveys are usually conducted over very large areas. Current analytical techniques are predicated on obtaining a sufficient sampling of the area under survey. This sampling includes both the number and location of data points. This consideration has a number of consequences for the survey in both design and execution. For example, the number and placement of both the seismic sources that generate seismic signals and the seismic receivers that detect the reflections are carefully considered and distributed across survey area.
Some surveys might employ several tens of seismic sources across several square kilometers. The analytical techniques mentioned above are usually also predicated on being able to distinguish which reflections are generated from which of the many seismic survey signals used in the survey. This, in turn, means that the seismic survey signals need to be distinguishable from one another.
One common technique for generating distinguishable seismic survey signals is to stagger the firing of the sources. The firing is then managed from some central point, typically a recording truck. The central source system sends commands to the seismic sources to fire them in a certain sequence and at certain times. This sequence and timing is predetermined and is not random.
However, this approach adds a logistical burden to the survey. The seismic sources are usually spread apart quite some distance, and typically at a goodly distance from the central source system. Running physical signal lines from the central source system to the seismic sources can be very difficult and costly both because of the time needed to run them and because of the logistics involved in transporting, deploying, and retrieving them. Some attempts have been made at implementing wireless surveys, but they encounter difficulties with reliability, bandwidth, latency, and/or reliability with respect to communications between the central source system and the seismic sources.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.